<p>The mantle transition zone (MTZ) is bounded by seismic discontinuities at average depths of 410 km and 660 km, which are generally associated with major mantle mineral transformations.&#160;A body wave impinging from above on these discontinuities develops a refracted and reflected branch, leading to multiple arrivals of the same wavetype within a short time window.&#160;These so-called triplicated body waves are observed at regional epicentral distances (15-30&#176;) and carry information on MTZ structure due to their strong interaction with the 410 km and 660 km discontinuities.&#160;Careful data selection and processing as well as the assessment of source parameters are necessary steps in obtaining a high quality triplication data set.&#160;In this study, we consider recordings of events in Central America at permanent and transportable USArray stations, which are inverted for mantle structure.&#160;Our methodology is based on a joint consideration of mineral physics and seismic data in a probabilistic inversion framework and allows for determination of mantle thermo-chemical and seismic velocity structure.&#160;We present constraints on the mantle structure underneath the Gulf of Mexico.</p>
Theoretical modeling of regular olivine grains misorientations in mimetic paramorphoses after ringwoodite and wadsleyite, the formation of which during the ascension of matter from the Mantle Transition Zone is expected, has been carried out. The coordinates of the misorientation axes and the misorientation angles, characterizing 10 operations of alignment in the pair intergrowths of olivine grains, eight of which are twins, are calculated. Possible conditions for the formation of mimetic paramorphoses predicted here, and the chances of their persistence are discussed. The calculated orientations are compared with the known twinning laws of olivine.
Waveform inversion for localized three-dimensional seismic velocity structure in the lowermost mantle beneath the Western Pacific